This invention relates to abrasive bodies, and more particularly to abrasive bodies which contain abrasive compacts.
Abrasive compacts are well known in the art and consist essentially of a mass of abrasive particles, generally present in an amount of at least 70%, preferably 80 to 90%, by volume of the compact, bonded into a hard conglomerate. Compacts are polycrystalline masses and can replace single large crystals. The abrasive particles of compacts are invariably superhard abrasives such as diamond and cubic boron nitride.
Abrasive compacts, particularly diamond and cubic boron nitride compacts, may be self bonded, i.e. the individual particles of the compact may be fused and bonded together without the aid of a metal or like bonding matrix. Alternatively, stronger and more durable compacts are produced when there is a suitable bonding matrix present.
In the case of cubic boron nitride compacts, i.e. compacts in which the abrasive particle is predominantly cubic boron nitride, the bonding matrix, when provided, preferably contains a catalyst (also known as a solvent) for cubic boron nitride growth such as aluminium or an alloy of aluminium with nickel, cobalt, iron, manganese or chromium. Such catalysts tend to be soft and to minimise smearing of the catalyst during use of the compact it is preferred that the matrix also includes a ceramic such as silicon nitride which is capable of reacting with the catalyst to produce a hard material.
In the case of diamond compacts, i.e. compacts in which the abrasive particle is predominantly diamond, the bonding matrix, when provided, preferably contains a solvent for diamond growth. Suitable solvents are metals of Group VIII of the Periodic Table such as cobalt, nickel or iron or an alloy containing such a metal.
For diamond and cubic boron nitride compacts the presence of a solvent or catalyst for the particular abrasive being used in the compact is desirable because then under the conditions necessary for the manufacture of such compacts intergrowth between the particles occurs. As is known in the art, diamond and cubic boron nitride compacts are generally manufactured under conditions of temperature and pressure at which the abrasive particle is crystallographically stable.
Diamond and cubic boron nitride compacts are used for the machining of metals and natural rock. In use, the compacts are bonded to a suitable support such as a shank to form a tool.
The compacts may be bonded to a backing such as a cemented carbide backing and then the backing bonded to the support to form the tool. Diamond and cubic boron nitride compacts bonded to a cemented tungsten carbide backing are described and illustrated in British Patent specifications Nos. 1,349,385, 1,407,393 and 1,489,130.
This invention is concerned with bonding a diamond or cubic boron nitride abrasive compact to another such compact or to a cemented carbide backing by means of an alloy bonding layer of a type similar to that described and claimed in British Patent specification No. 1,489,130.